c++ virtual function reimplementation

even i think that question is stupid. but i've a little experience.

i have a base class that has such method:

class A{  virtual void func(int)=0 };

and inherited class

    class  B :public A
  {  
     //how should i write?
    //a  
       virtual void func() {    implementation...}  

    //b
      void func() {implementation    } 
   //my target is to redefine a function of ansestor
 //i worry that variant b can  cover ansestor function and i will not redefine it
 //but what if i don't want that the function that was virtual i开发者_JAVA百科n ansestor, will   be      virtual in subclass? 
i'm confused
}

i don't know that to do. if i don't need this virtual function complete

You ask, "what if i don't want that the function that was virtual in ansestor, will be virtual in subclass?"

Sorry, but every function that is declared virtual in a base class, is also virtual in all derived classes.

It actually doesn't matter whether you use the virtual keyword in the derived-class declaration. Options a and b are identical -- in both cases B::func is virtual.

I suggest your write two small programs, one for each implementation to determine which suits your needs.

In C++ the function signature consists of the function name and function arguments. In a class you cannot have two functions with same signature. So your second (non-virtual) function declaration will generate compiler errors.

In short:

virtual void func() { //implementation}

and

void func() { //implementation }

have the same signature and cannot be declared in the same class.

Virtual means that reimplementation is possible in inherited class(es). Virtual function will allways be virtual no matter the depth of inheritance.